Solar Energy - Why Has Domestic Rooftop Pv Dominated over Utility Scale Pv

1 - Why has domestic rooftop PV dominated over utility scale PV,[pic 1]

and will that trend continue?

The major difference between the domestic rooftop PV and the utility scale PV is that they are two different

kind of offer. The rooftop PV have the advantage to offer a not common kind of electricity, the one you product

yourself. Thanks to that the client look at the prices but not such as an electricity company would do. There

could be a trendy movement as well. On the other hand, the utility scale PV has to enter the market with all

the other technologies. Like represented in the figure 1, in term of price it is hard to be as cheap.

Figure 1: Levelised cost of electricity generation by technology [Source 5]

In order to become really competitive, the solar panels face three barriers:

• A technical barrier.

An efficiency constraint of 4–12% for thin film and under 22% for crystalline and a performance limitation

trough power conditioning system (e.g. batteries, inverters)

• An economic barrier.

A high initial cost and a critical financing. Financial institutions consider solar technologies as at high

risk because of its short history.

• An institutional barrier.

There is a lack of effective and appropriate laws.

An advantage of the PV rooftop panel in comparison with the utility scale PV is the save of money save with

the transmission and distribution (see figure 2).

As represented in the figure 3, the price of the solar panel is continiously decreasing. Thus in the futurek utility

scale PV are going to be more competitive. The balance between the rooftop and the utility scale one will be

consequently influenced by the evolution of the solar policies (feed-in tariff, green credits, ...)

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Figure 2: Solar PV costs for different size of installation (2008 US$/MWh). [Source 4][pic 2][pic 3][pic 4]

Figure 3: The global PV module price learning curve for c-si wafer-based and CdTe modules [Source 6]

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2 - PV battery optimisation.[pic 5][pic 6]

This model used in Chris Cooper spread sheet calculate at each hour the solar generation, the electricity bought

to the grid and the electricity produced by the panel which is sell to the grid, stored in the battery and consumed.

All these outputs are function of different parameters like the daily household energy use, the solar PV system

size, the household load profile, the battery size and cost, the feed-in tariff, ... By making the balance sheet of

these the net annual benefit of a solar PV installation combined to a battery can be found.

In order to make the model easy to play with and understandable, different non-negligible assumption have

been made:

• There is no assumed degradation of solar output or battery round-trip efficiency over time.

• The life of the battery and the solar panels are the same (parameter of the model). Batteries deteriorate

normally quickly than pannels.

• The whole consumption is based on an averaged one-day data.

• Each decision about the electricity consumption and storage is taken at each hour. That is thus not

optimised.

Trying to find the optimum size of the battery using the excel solver leads to run without any battery. To have

an idea about in which case a battery is less bad, a study about the household load profile style, the region and

the amount consumed influence have been realised. The results are available in figure 8, 9 and 10. The datas